Among various existing real time information service approaches, it is common to arrange a call center for a called party (a called user, also known as a called terminal or a callee). The call center allocates different service access numbers for different information service fields. A calling party (a calling user, also known as a calling terminal or a caller) sends a corresponding call request as needed to thereby establish a session with a corresponding called party over the call center.
A single service window loss queuing model M/M/1/1 is generally adopted for existing voice call services, where M denotes a probability distribution, i.e., a negative exponential distribution (random calls of users typically comply with a negative exponential distribution in a general call model). In single service window loss queuing model M/M/1/1, the first “M” refers to that a probability distribution of an interval of time T at which different calling users initiate successively calls complies with a negative exponential distribution with a parameter “λ”, and the second “M” refers to that a probability distribution of a communication period of time T consumed for a user complies with a negative exponential distribution with a parameter “μ”. In the M/M/1/1 model, the first “1” refers to the number of service window(s), that is, a called user is in communication with only one calling user at a time, and the second “1” refers to the maximum queue capacity containing users who are being served or queuing, that is, only one calling user is allowed to be served at a time. FIG. 1 illustrates a specific status flow chart, where “0” denotes an idle service window and “1” denotes a busy service window. According to the existing single service window loss queuing model M/M/1/1, a calling user will give up automatically the chance to be served when the calling user finds that the called user is busy, so that a plurality of calling users who are calling the same called user are not aware of a current queuing condition of the called user according to the existing single service window loss queuing model M/M/1/1.
There is another call queuing method in the prior art, for example, as disclosed in the application No. CN 200410038332.5, and in this call queuing method, a calling user will be enqueued automatically in a private queue of a called user when the called user is determined to be in a “busy” status or will be connected to the called party when the called user is idle. Although this call queuing method can enable automatic queuing in the private queue of the called user when the called user is in a “busy” status to thereby increase the number of enqueued users as compared with the first call approach in the existing single service window loss queuing model M/M/1/1, this call queuing method can provide no relevant message notification. According to this call queuing method, a calling user can only be temporarily stored in the private queue of a called user until the called user is available to be connected to the calling user, so that the calling user still can not acquire its condition of being queued for the called user but wait blindly.
It is possible in the prior art to enable communication between users, to provide information on an idle or busy status of a called terminal and to notify through voice a calling terminal about an idle or busy status of the called terminal when no communication has been established between the calling terminal and the called terminal. Unfortunately, when a plurality of calling users wish to establish communication with the same called user, for example, a calling user 1, a calling user 2, . . . , and a calling user 5 wish to establish call connections with a called user A successively, if the called user A is in communication with the calling user 1, then the reset calling users 2-5 have to wait, and the calling users 2-5 can not determine whether it is necessary to continue with waiting although they are aware of ongoing communication of the called user A and acquire the busy status of the callee, so that the calling user 5, for example, with a relatively large number of preceding waiters will waste a period of time on waiting, and a calling user with few preceding users, e.g., the calling user 2, is not aware of the number of preceding waiters and thus may improperly cancel waiting, which may influence a demand of the calling user.